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NVD / CVE Program· CNA Linux

CVE-2025-40173: net/ip6_tunnel: Prevent perpetual tunnel growth

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.15% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 10fe967efe73c610e526ff7460581610633dee9c, 11f6066af3bfb8149aa16c42c0b0c5ea5b199a94, 21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16; azl3 kernel 6.6.112.1-2 on Azure Linux 3.0 6.6.117.1-1.

Low priority for now. Upgrade to Linux Linux 10fe967efe73c610e526ff7460581610633dee9c, 11f6066af3bfb8149aa16c42c0b0c5ea5b199a94, 21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16; azl3 kernel 6.6.112.1-2 on Azure Linux 3.0 6.6.117.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: net/ip6_tunnel: Prevent perpetual tunnel growth Similarly to ipv4 tunnel, ipv6 version updates dev->needed_headroom, too. While ipv4 tunnel headroom adjustment growth was limited in commit 5ae1e9922bbd ("net: ip_tunnel: prevent perpetual headroom growth"), ipv6 tunnel yet increases the headroom without any ceiling. Reflect ipv4 tunnel headroom adjustment limit on ipv6 version. Credits to Francesco Ruggeri, who was originally debugging this issue and wrote local Arista-specific patch and a reproducer.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Nov 12, 2025
Updated
Oct 19, 2026
EPSS
0.1% · 4th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-40173

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 4.7affected
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before 566f8d5c8a443f2dd69c5460fdec43ed1c870c65affected · git
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before 11f6066af3bfb8149aa16c42c0b0c5ea5b199a94affected · git
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before 402b6985e872b4cf394bbbf33b503947a326a6cbaffected · git
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before 10fe967efe73c610e526ff7460581610633dee9caffected · git
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before 48294a67863c9cfa367abb66bbf0ef6548ae124faffected · git
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before eeb4345488672584db4f8c20a1ae13a212ce31c4affected · git
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before b6eb25d870f1a8ae571fd3da2244b71df547824baffected · git
    • 8eb30be0352d09165e94a41fef1c7b994dca0714 and later · before 21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16affected · git
    • before 4.7not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.158-16.1.158-1
Debian:13linuxbefore 6.12.57-16.12.57-1
Debian:14linuxbefore 6.17.6-16.17.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2025-40171Nov 12, 2025 · nvmet-fc: move lsop put work to nvmet_fc_ls_req_op
    30Monitor
  • ← EarlierCVE-2025-40172Nov 12, 2025 · accel/qaic: Treat remaining == 0 as error in find_and_map_user_pages()
    31Monitor
  • Later →CVE-2025-40174Nov 12, 2025 · x86/mm: Fix SMP ordering in switch_mm_irqs_off()
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux10fe967efe73c610e526ff7460581610633dee9cVendor (CNA)
Linux Linux11f6066af3bfb8149aa16c42c0b0c5ea5b199a94Vendor (CNA)
Linux Linux21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16Vendor (CNA)
Linux Linux402b6985e872b4cf394bbbf33b503947a326a6cbVendor (CNA)
Linux Linux48294a67863c9cfa367abb66bbf0ef6548ae124fVendor (CNA)
Linux Linux566f8d5c8a443f2dd69c5460fdec43ed1c870c65Vendor (CNA)
Linux Linuxb6eb25d870f1a8ae571fd3da2244b71df547824bVendor (CNA)
Linux Linuxeeb4345488672584db4f8c20a1ae13a212ce31c4Vendor (CNA)
azl3 kernel 6.6.112.1-2 on Azure Linux 3.06.6.117.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.158-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records